The given matrix is x1x2x3y1y2y3111 using R2 → R2−R1 , R3 → R3−R1 Δ = x1x2−x1x3−x1y1y2−y1y3−y1100 = 0 (Since points are col linear i.e., area of triangle = 0) ⇒ x2−x1x3−x1y2−y1y3−y1 = 0 So, the rank of matrix is always less than 2.